The Internet and social media are playing a very important role in the search for a missing Nelson County teenager.  

Alexis Murphy, 17, has been missing since Saturday. She left her home in Shipman that evening, reportedly headed for Lynchburg. According to Nelson County Sheriff David Brooks, surveillance video shows Murphy at the Liberty gas station in Lovingston Saturday at 7:15 p.m. That's the last time she was seen. Police found her abandoned car Tuesday between 8 p.m. and 9 p.m. at Carmike 6 movie theater in Charlottesville.

The National Center for Missing and Exploited Children is now assisting law enforcement in the Alexis Murphy case. Alexis' picture is on the center's website.

Senior Division Director Robert Lowery talked with us via Skype Thursday about how important it is to have so many agencies involved early in the game.

"Because of the circumstances of her disappearance, we have to assume she is in critical danger so therefore we cannot waste time. That's why you're seeing a massive search underway right now," said Lowery.      

Murphy is now one of the 288 children missing in Virginia.

Social media sites like Twitter and Facebook are also aiding authorities in their search for Alexis - and on day five of the search, word of her disappearance has reached millions.

Facebook, Tumblr and Twitter are all trending with pleas to help find Alexis. The presence of that message and her picture could help answer questions in her case. 

"It raises awareness to that person who stops at a gas station, who happens to see her if she happens to be there can report that in," said Marijean Jaggers, social media expert. 

Jaggers says, in missing persons cases, the faster the information gets out the better. 

"People taking that kind of information to a community that's active, that's quick acting, that can really mobilize very, very quickly, is smart," said Jaggers. 

Since her disappearance, Alexis has gained thousands of followers on Twitter who are retweeting and reposting her picture.  Famous rapper Wale also retweeted a plea to find Alexis to some three million followers. 

In addition to spreading the word, social media is also giving investigators an idea of Alexis' actions in the days leading up to her disappearance.

"We look at their tweets to see if they're tweeting about meeting somebody. There are a lot of different things that we would look at," said Lt. Todd Hopwood of the Albemarle County Police Department. 

That's especially true for someone like Alexis who is very active on Twitter - one of her last tweets 'burg bound' shared her plans to head to Lynchburg the day she disappeared. 

But the social media attention can also be overwhelming for police who have to check out every tip.

"It sometimes can be a drain on our resources but we want to get all that information in so we do appreciate people spreading the word," said Hopwood. 

Although social media can help police gain insight, the most useful function is raising awareness and getting someone with information to come forward, which is exactly what Alexis' family is asking the public to do. 

If you have any information, authorities are asking you to call 434-263-7050.